Methods

Darting techniques - update: 13 Sep 2010
A method was developed to use the reticle of the Zeiss [Diavari V3-12x56T] telescope, mounted on the dart gun, to estimate the distance of a lion from the dart gun. Accurate range estimation is crucial to successful dartings, especially under low-light conditions or in darkness, when most of dartings occur. Detailed measurements were collected from several adult lionesses of the perpendicular view of body length, chest height and shoulder width.

 

 

 

 

 

 

A shape of a lion was constructed with these measurements (see below) and were placed at distances ranging from 20 to 50 metres from the dart gun (at 10 metre intervals). The images observed through the telescope were photographed.

Telescopic view at 30 m Telescopic view at 50 m Telescope reticle The telescope images were edited to produce a field guide of the size of an adult lioness in relation to the telescope reticle, when viewed at 20, 30 40 & 50 metres. Most lions are darted from distances of between 30 and 45 metres.

20 metres

30 metres

40 metres

50 metres

Large carnivores, such as lions, are generally difficult to study, especially in a desert environment such as the Kunene Region. Lions, like all other felids, are "stalkers" - they make use of cover and camouflage to stalk up to their prey, followed by a quick final rush. As a result, lions are difficult to locate and spot in the vastness of the Namib Desert. The two examples below illustrate how they use the habitat and blend into their environment.

Can you spot the lion in the two pictures? Move your mouse over the lion and press the left button to see if you are right.

The study area is covered systematically by tracking spoor, setting out bait and using sound playbacks to locate and capture individual lions. Adult and sub-adult lions are captured and individually marked with a hot brand, and several lions in each sub-group are marked with a radio collar. (Click on photos to view enlargement)

A light aircraft is used to systematically locate radio-collared animals. Aerial locations are followed-up by ground observations to record group composition in relation to individuals and age/sex structure, and the ratio of marked to unmarked individuals. Life tables are constructed and updated to compute survivorship and mortality rates. The population dynamics of lions are evaluated by monitoring, since 1999, a core group of 13 radio-collared lions. These analyses include several population parameters, such as birth rates, mortality, fecundity, exponential rate of increase, and age-specific survivorship. Home range analyses are based on locating the daytime resting spots of lions by radio telemetry, with at least 24 hours between fixes. Home range size is calculated using the Minimum Convex Polygon (MCP) and Kernel Contour methods (Harris et al. 1990).

Video (to view download QuickTime)

Darting of young male lion in Mudorib River (2001)

dartlion.mov 00'07 / 664Kb